This invention relates to an apparatus for controlling an internal combustion engine of an automotive vehicle and, more particularly, to such an engine control apparatus for terminating delivery of fuel to the engine in selected modes of engine operation.
Various engine control apparatus have been proposed in the past for terminating delivery of fuel to an internal combustion engine in selected modes of engine operation, but such prior apparatus have demonstrated very poor fuel economy.
A conventional engine control apparatus includes a solenoid valve provided in a fuel conduit through which fuel is delivered to an internal combustion engine. The solenoid valve is connected a potential source through a parallel circuit of a clutch switch which is closed when the clutch is disengaged, a neutral switch which is closed when the transmission is in neutral, a throttle switch which is closed when the throttle valve opens over a predetermined angle, and a relay switch which is closed when the vehicle speed exceeds a predetermined value. The solenoid valve closes to terminate fuel delivery to the engine only when all of these switches are open. Therefore, such a conventional apparatus cannot save unnecessary fuel when the clutch is disengaged, the transmission is in neutral, or the vehicle is at rest.
A second type of conventional engine control apparatus includes a clutch pedal switch for generating a signal indicative of the clutch pedal being depressed, a vehicle speed sensor for generating a signal indicative of the vehicle being running, and a control circuit for connecting the ignition system to a power source in response to the signal from the clutch pedal switch or the signal from the vehicle speed sensor. The control circuit disconnects the ignition system from the power source to bring the engine to a stop in the absence of the signal from the clutch pedal switch and the signal from the vehicle speed source. Therefore, such a conventional apparatus cannot save unnecessary fuel during deceleration.
Furthermore, for automotive vehicles employing a brake booster which utilizes vacuum created in the intake manifold of the engine in applying brakes to the vehicle, the vacuum in the brake booster will fall to a level insufficient for application of braking to the vehicle when the brake pedal is depressed several times after fuel delivery to the engine is terminated to bring the engine to a stop. This results in failure to ensure safety during vehicle running.
The present invention provides an improved engine control apparatus which can save unnecessary fuel in selected modes of engine operation to achieve more fuel economy and less exhaust emission and which can maintain brake booster vacuum level sufficient for application of braking to assure safety during vehicle running.